Shut-off flaps are widely used shut-off elements in water management. In comparison to slide gate valves, flaps are very compact and especially in nominal sizes greater than DN 300, require substantially less installation space. Therefore, pipeline systems with nominal sizes beyond ca. DN 300 are mostly equipped with shut-off flaps. The disadvantage of shut-off flaps is to be found in that the flap disk is located directly in the flow. Since, in the closed position, the flap disk must withstand the differential pressure of the system, the flap disks must be made correspondingly thick, especially for high differential pressures. The greater (thicker) the dimensions of the flap disk, however, the more the throughflow resistance that it opposes against the medium.
From EP 1 427 955 A1 is known a generic shut-off flap with a flap-shaped shut-off element that can swivel around a rotation axis within a housing. In this known shut-off flap, the flap-shaped shut-off element is made in an eccentric construction with a flap disk, staggered relative to the rotation axis, and with lateral hubs to hold drive shafts supported in the housing. With such shut-off elements, the hubs in the flow, however, can produce a wake space, depending on shape and width, which causes vortexes in the outflow area. These vortexes can, on the one hand, increase the wake area and thus increase to total resistance of the shut-off flap and, on the other hand, form vortex fields, which lead to the vibration stimulation of the shut-off flap or of the following pipeline.